It may readily be understood and not difficult to calculate the energy delivery (kWh) at a particular site of an individual renewable energy technology based on a renewable resource, e.g., sun, wind or biomass, inter alia. However, when considering the supply of a periodic, e.g., annual, load at a site, and incorporating there the implementation of more than one energy supply source, particularly when, for example, implementing multiple renewable technologies, a complication is to account for the interactions between the multiple energy systems, renewable or otherwise, relative to the load. In particular, there may be times when some renewable energy, whether from one or a combination of renewable sources, will be generated in excess of the load and may thus be credited at a lower value; but alternatively, often there will be times when some energy must be purchased from a utility because the renewable energy measures are not sufficient to meet the load.